IGBT paralleling Zhou Yizheng Current sharing o Static

IGBT paralleling Zhou Yizheng

Current sharing o Static current sharing ¬ Affect conduction losses distribution o Dynamic current sharing ¬ Affect dynamic losses distribution and dynamic stress Set date Copyright © Infineon Technologies 2010. All rights reserved. Page 2

Parameters effecting current balance Static sharing X Commutation loop impedance AC loop impedance X Thermal X Set date X X Driver symmetry Module static parameters Dynamic sharing X Module switching parameters X Magnetic field X Communicating loop: dynamic & static current sharing AC loop: static current sharing Copyright © Infineon Technologies 2010. All rights reserved. Page 3

Test set up Module: FZ 1500 R 33 HE 3. ¬ Channel 1 IGBT module 1 collector current ¬ Channel 2 IGBT module 2 collector current ¬ Channel 3 IGBT module 1 gate voltage ¬ Channel 4 IGBT module 2 gate voltage Set date Copyright © Infineon Technologies 2010. All rights reserved. Page 4

Bus bar symmetry Symmetrical Busbar Additional stray impedance applied Stray impedance in the commutation loop influence both dynamic current sharing and static current sharing. (low impedance high current)

Bus bar symmetry Symmetrical AC path Unsymmetrical AC path have no influence to turn on dynamic current sharing, it influence the static current sharing, further influence the turn off dynamic current sharing and current redistribution. (low impedance high current)

Bus bar symmetry 20 degree 20 degree 40 degree Thermal symmetry influence static current sharing and , but it is not so strong. (high temperature low current). Thermal symmetry have almost no influence to turn on current sharing, but can influence turn off current sharing

Magnetic field Inductor outside the SB Inductor Right side in SB Inductor Left side in SB Inductor influence for active board Driver Outside the SB Driver inside the SB Inductor influence to passive board

Magnetic field For FZ+FZ double pulse test setup: o Cable connection inside bus bar influence both static current sharing and current redistribution(created magnetic field influence bus bar impedance), but almost no influence at turn on. o Magnetic filed of inductor can influence current redistribution and driver (if the driver is passive adaptor board based) further influence turn on current sharing and current redistribution. o If active adaptor board based driver is used, magnetic filed of inductor have almost no influence on turn on current sharing

Driving conecpt Isolated o Each IGBT have its own isolated driver core Active adopt board o One driver core with booster circuit on adaptor board Passive adopt board(separate Rg) o One driver core with separate gate resistor on adaptor board Passive adopt board(merged Rg) o With gate resistor on driver core, just cable to connect IGBT module gate Set date Copyright © Infineon Technologies 2010. All rights reserved. Page 10

Driving concept Isolated Active Symmetrical bus bar Merged Rg Separate Rg

Driving concept Isolated driver Unsymmetrical bus bar Passive separated Rg

Cable length Merged Rg 20 cm / 20 cm 20 cm / 100 cm 101 cm / 100 cm Separate Rg 20 cm / 20 cm

Cable length Merged Rg 20 cm / 20 cm 20 cm / 100 cm 101 cm / 100 cm Separate Rg 20 cm / 20 cm Ic 1 Right IGBT Ic 2 Left IGBT Vge 1 Left IGBT Vge 2 Right IGBT

Driving Different driver concept shows almost similar turn on/off performance, at precondition that system is symmetry. o Active board shows a little bit poorer turn on current sharing performance o Passive board shows high amplitude of current redistribution and oscillation frequency In unsymmetrical system, isolated driver shows better turn on dynamic current sharing and almost similar turn off dynamic current sharing. Separate Rg shows better dynamic current sharing than merged Rg, if gate cable is unsymmetrical.

Module parameters Vcesat, Vf o Influence static current sharing Vth, Vp o Influence dynamic

Module parameters Same Vcesat class Set date Same Vcesat class Copyright © Infineon Technologies

Module parameters Vcesat 3. 33 3. 31 Vcesat 3. 34 3. 31 Vcesat 3. 31 3. 37 Vth 5. 90 Vth 5. 86 5. 90 Vth 5. 90 Vp 10. 33 10. 28 Vp 8. 93 10. 28 Vp 10. 33 10. 23 Different Vcesat class(+/-1) almost show no influence to static current sharing. positive temperature coefficient + round up/down Different module have quite small influence to module dynamic current sharing(current redistribution).

Conclusion Set date Copyright © Infineon Technologies 2010. All rights reserved. Page 20

Conclusion System symmetry is at first priority (including commutation loop symmetry, AC path symmetry and AC output cable position). Based on symmetrical system, either isolated driver or active adaptor board or passive adaptor board all can get very good current sharing results. If cable length for passive adaptor is not same, separated Rg and emitter Rg is recommended. Module influence to current sharing is quite small. IGBT Vcesat class +/-1 is quite Ok for current sharing. It’s better to take same Vf class module. System magnetic field effect need to be care about